Signal repeater and re-driver circuits are used in networking, communication, computer, and a variety of other systems. Upstream chips may have a limited drive capability, limiting the distance that signals may be safely driven. Standards such as Peripheral Components Interconnect Express (PCIE) and others may specify a limit to the length of a signal line.
A long-distance line may be divided into two or more segments, with a buffer, re-driver, or repeater between segments. A re-driver chip may be used to receive the signal from a first segment, regenerate the signal, and output the signal to the next segment. A wide variety of simple buffer chips are available. However, modern signals are often differential, small-voltage-swing signals. Buffers must not distort the signal's characteristics. Thus specialized differential re-drivers may be needed that are very sensitive to small-swing signals.
Communications sometimes occurs across longer lines known as transmission lines. When the speed or frequency of signaling increases, shorter line lengths act as transmission lines. Special layout and termination of transmission lines is often needed to minimize reflections and optimize performance.
The shape of the waveform being driven onto the transmission line as an input can be adjusted to improve performance. The initial portion of the waveform can be increased in amplitude relative to the rest of the waveform, which is known as pre-emphasis.
What is desired is a re-driver integrated circuit (IC) that is designed for repeating small-swing signals. A re-driver that compensates for transmission-line effects is desirable. A re-driver chip that boosts output signals using pre-emphasis is desirable. A re-driver chip that also shapes, amplifies, and equalizes signals to improve signal characteristics is also desirable.